SiC does not become a liquid phase under a normal pressure, which is different from Si. Therefore, a SiC substrate cannot be manufactured by using a pulling method, which is used for forming a Si substrate. There is an attempt to perform SiC substrate growth by a sublimation re-crystallization method for changing a solid phase to a gas phase directly. However, in this case, enormous inventive approach is necessary for forming the SiC substrate with high quality and large diameter.
Regarding the above point, it is reported that 3C—SiC (or β-SiC) material having a cubic crystal can be grown on a {111}-surface of the Si substrate. For example, it is disclosed in Japanese Patent Application Publication No. 2003-68654. Specifically, a groove, i.e., an undulation, along with one direction is formed on the Si substrate. A SiC material is grown on a surface having a relief caused by the groove, so that the SiC crystal having low surface defect density is obtained.
The Japanese Patent Application Publication No. 2003-68654 discloses that the SiC material is epitaxially grown on the Si substrate. Therefore, a diameter of the substrate depends on the Si substrate, so that it is considered that a diameter of the SiC substrate can become large.
However, when a semiconductor substrate (i.e., a 3C—SiC/Si substrate) having a 3C—SiC layer formed on a Si substrate is used for manufacturing a power device, a band offset exists at the interface between the 3C—SiC layer and the Si substrate. Thus, a voltage drop of a few volts is generated. Therefore, a problem arises that the manufactured power device includes a few voltage drop.